Generally, an optical connector used for butt-jointing multiple optical fibers or connecting optical fibers with various optical devices has optical fiber plugs into which the optical fibers are inserted. A conventional optical fiber plug is cylindrically shaped and made of a low expansion material with an excellent wear resistance, such as zirconia ceramics. In a central portion of the connecting end surface of the optical fiber plug, a leading end surface of the optical fiber is exposed. The connecting end surface is formed to have a convex spherical surface with a radius of curvature of about 20 mm.
PTL 1 discloses a polishing apparatus for processing a connecting end surface of an optical fiber plug to have a convex spherical surface with a predetermined curvature. The polishing apparatus disclosed in PTL 1 has a polishing disk having a polishing film adhered to its surface via an elastic sheet and being supported so as to enabling a circular motion in a predetermined plane, and a slider having a plug holder to which an optical fiber plug is mounted. This polishing apparatus reciprocates the slider with respect to the polishing disk while causing the circular motion of the polishing disk in the state where a connecting end surface of an optical fiber plug is pressed against the polishing disk, so that the connecting end surface of the optical fiber plug is polished.